libcriu: use swrk by default

Not sure if it is okay, but this patch breaks backward compatibility,
as we now discourage people from using criu as a system service by default.
But it is better to be done rather sooner than later, considering criu service
is not widely used.

On a patch side, we just need to daemonize swrk if self-dump is requested.

Signed-off-by: Ruslan Kuprieiev <rkuprieiev@cloudlinux.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>